The present invention relates to a piston nest. In particular, the present invention relates to a piston nest that can securely individually nest a plurality of pistons, such as syringe pistons, prior to automated assembly of the pistons to syringes.
A piston nest is typically a substantially planar tray having a plurality of individual nesting units each capable of receiving a syringe piston. The piston nest is typically used in automation processes for the assembly of e.g., pre-filled syringes. In operation, the piston nest is placed above a similarly oriented tray of pre-filled syringe barrels and then each of the pistons from the piston nest are pressed into the aligned underlying syringe barrels by an automated means, such as with automated mechanical pins. The mechanical pins function to push each of the syringe pistons out of the piston nest and into the underlying individual syringe barrels.
A partial cross-sectional view of an individual nesting unit of a conventional piston nest is shown in FIG. 1. As shown in FIG. 1, the piston nest 1100 is configured such that the syringe piston 1102 rests within a single nesting unit 1104. The syringe piston 1102 is retained within the single nesting unit 1104 by an inwardly extending flange portion 1106 located at the bottom of the piston nesting unit 1104. In such a piston nest configuration, the syringe piston 1102 is only retained within the single nesting unit 1104 by gravity. As such, the piston nest 1100 must be constantly maintained in the proper orientation i.e., the upright position, shown in FIG. 1, in order for the syringe piston 1102 to remain within the single nesting unit 1104. Otherwise, the syringe piston 1102 will be prone to “fall out,” become “cocked” or otherwise escape from the single nesting unit 1104. This is especially troublesome when the piston nest 1100 is configured with a large number e.g., one hundred (100) single nesting units per piston nest, which is typically the case. Moreover, in order to properly assemble the syringe piston 1102 into syringe barrels (not shown), the syringe piston 1102 must be properly oriented in the piston nest 1100 i.e., not cocked or otherwise jammed within the single nesting unit 1104.
FIGS. 2A and 2B illustrate another individual nesting unit of a conventional piston nest 1200 and syringe piston 1202 manufactured by Daikyo Seiko, Ltd. The piston nest 1200 however, has a single nesting unit 1204 configured to specifically mate with the Daikyo syringe piston 1202. In particular, the single nesting unit 1204 includes a retention rib 1206 about a midpoint along the length of the nesting unit 1204 which is designed to specifically mate with an annular recess or groove 1208 of the syringe piston 1202. Consequently, the piston nest 1200 cannot be used with any other syringe piston designs besides the Daikyo syringe piston 1202. Moreover, the single nesting unit 1204 is limited to a single point contact retention means for securing the syringe piston 1202 within the piston nest 1200. Such single point contact retention means renders the syringe piston 1202 susceptible to cocking or displacement within the single nesting unit 1204 that may result from mishandling of the piston nest 1200. This is especially important because, for example, with one hundred single nesting units per piston nest 1200, if a single syringe piston 1202 is out of alignment, the entire piston nest 1200 must be discarded. Accordingly, there is still a need for a piston nest that can reliably hold and retain a plurality of syringe pistons and that addresses the above-described deficiencies of conventional piston nests.